1 files changed, 55 insertions, 0 deletions
diff --git a/src/noffer.js b/src/noffer.js
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+++ b/src/noffer.js
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+// CLINK offer codes (`noffer1…`) — a static, nostr-native payment code.
+// Bech32 over TLV: 0 = service pubkey (32B), 1 = relay url, 2 = offer id,
+// 3 = pricing type (2 = payer chooses the amount). A payer decodes this,
+// sends a NIP-44-encrypted kind-21001 request to the pubkey via the relay,
+// and gets an invoice back — no web server involved.
+
+import { bech32 } from '@scure/base';
+import { hex } from '@scure/base';
+
+const te = new TextEncoder();
+const td = new TextDecoder();
+
+function tlv(items) {
+  const parts = [];
+  for (const [type, value] of items) {
+    if (value.length > 255) throw new Error('tlv value too long');
+    parts.push(new Uint8Array([type, value.length]), value);
+  }
+  const total = parts.reduce((n, p) => n + p.length, 0);
+  const out = new Uint8Array(total);
+  let off = 0;
+  for (const p of parts) { out.set(p, off); off += p.length; }
+  return out;
+}
+
+export function encodeNoffer({ pubkey, relay, offerId, priceType = 2 }) {
+  const data = tlv([
+    [0, hex.decode(pubkey)],
+    [1, te.encode(relay)],
+    [2, te.encode(offerId)],
+    [3, new Uint8Array([priceType])],
+  ]);
+  return bech32.encode('noffer', bech32.toWords(data), 2000);
+}
+
+export function decodeNoffer(str) {
+  const { prefix, words } = bech32.decode(String(str).trim(), 2000);
+  if (prefix !== 'noffer') throw new Error('not an offer code');
+  const data = bech32.fromWords(words);
+  const out = {};
+  let off = 0;
+  while (off + 2 <= data.length) {
+    const type = data[off], len = data[off + 1];
+    const value = data.slice(off + 2, off + 2 + len);
+    off += 2 + len;
+    if (type === 0) out.pubkey = hex.encode(value);
+    else if (type === 1) out.relay = td.decode(value);
+    else if (type === 2) out.offerId = td.decode(value);
+    else if (type === 3) out.priceType = value[0];
+    else if (type === 4) out.priceSats = [...value].reduce((n, b) => n * 256 + b, 0);
+    else if (type === 5) out.currency = td.decode(value);
+  }
+  if (!out.pubkey) throw new Error('offer code has no pubkey');
+  return out;
+}